There exist a great number of methods and devices for measuring by optical means either an angle of incidence of a luminous beam or distances between an object and a detector. For the measurement of great distances and of great accuracy, one uses normally a laser by means of which one executes either a measurement of time for objects at great distances or an analysis of interference fringes for obtaining a great precision. For the measurement of short distances and on machines where a very great accuracy is not required, one works generally in accordance with the principle of triangulation which will be described hereunder, according to FIG. 1. This principle of triangulation necessitates an important base for obtaining a sufficient accuracy and this gives rise principally to a strong limitation of the measuring range due to the determined optical arrangement. These disadvantages are particularly annoying in the case where one is obliged to arrange the whole within a transducer of the smallest possible dimensions, in order to fix it on a machine tool or similar. This transducer must comprise the source of light and the receiver if possible in the same housing, the space taken of which must be as small as possible because the space at disposal is often very limited.